Ni Zn Nanoferrites Research Articles

Structural and dielectric properties of Cr-doped Ni–Zn nanoferrites

Cr-doped Ni–Zn ferrite nanoparticles having the general formula Ni0.5Zn0.5CrxFe2−xO4 (x=0.1, 0.3, 0.5) were prepared by the simplified sol–gel method. The structural and dielectric properties of the samples sintered at 750±5 °C were studied. X-ray diffraction (XRD) patterns confirm the single-phase spinel structure of the prepared samples. The crystallite size calculated from the most intense peak (3 1 1) using the Debye–Scherrer formula was 29–34 nm. Scanning electron microscope images showed that the particle size of the samples lies in the nanometer regime. The dielectric constant (εr), dielectric loss tangent (tan δ) and ac electrical conductivity (σac) of nanocrystalline Cr–Ni–Zn ferrites were investigated as a function of frequency and Cr concentration. The dependence of εr, tan δ and σac on the frequency of alternating applied electric field is in accordance with the Maxwell–Wagner model. The effect of Cr doping on the dielectric and electric properties was explained on the basis of cations distribution in the crystal structure.

Ni-Zn Nanoferrites Synthesized by Microwave Energy: Influence of Exposure Time and Power

This paper describes the synthesis of Ni-Zn nanoferrites by combustion reaction using microwave energy as a heating source, and evaluates the performance of these materials as absorbers of electromagnetic energy at frequencies between 4 - 12 GHz. The influence of the synthesis conditions on the structure, morphology and absorption characteristics was investigated. The powders were characterized by DRX, BET, AGM and reflectivity measurements in the frequency bands of 8 to 12 GHz. The XRD results show the formation of Ni-Zn ferrite phase and Fe2O3 and Ni as secondary phases. The crystallite sizes ranged from 32 to 42 nm. The parameters of exposure time and power of the microwave oven changed the final characteristics of the resulting powders. The morphology of all the powders consisted of soft nanoparticle agglomerates. The best saturation magnetization and attenuation results were 70 emu/g and -4.1 dB in the frequency of 10 GHZ.

Mössbauer investigation on Ni–Zn nanoferrite with the highest saturation magnetization

The highest value of saturation magnetization (80 emu/g) ever reported has been achieved in Ni0.65Zn0.35Fe2O4 at lower sintering temperatures through sol-gel synthesis. The observed highest value of saturation magnetization has been explained on the basis of core-surface magnetic interactions facilitated through low temperature and in-field Mössbauer investigation of the system. Cation distribution for this composition has also been proposed and verified quantitatively by calculating the intensity of each peak of x-ray diffraction and estimating the lattice constant.

ChemInform Abstract: Development of Ni—Zn Nanoferrite Core Material with Improved Saturation Magnetization and DC Resistivity.

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Development of Ni–Zn nanoferrite core material with improved saturation magnetization and DC resistivity

Nanostructured Nickel–Zinc ferrite of composition Ni 0.65Zn 0.35Fe 2O 4 was prepared by sol–gel, co-precipitation, citrate-gel and oxalate precursor methods. X-ray diffraction (XRD) patterns of all the samples showed the spinel structure. A comparison of average crystallite size clearly indicated that the sol–gel method was the effective one in producing small crystallite sized samples having insignificant variation with annealing or sintering temperatures. Also, sol–gel method was observed to provide high saturation magnetization values in samples sintered even at lower temperatures. The high magnetization values are, in general, reported in bulk samples prepared at higher sintering temperatures by conventional ceramic method. Direct-current (DC) resistivity of these samples was also considerably improved as compared to that of the bulk materials. Discussion has been made on the basis of observed higher values of saturation magnetization and dc resistivity towards the development of a high-quality core material useful for high-frequency applications.